Authentication of users of computer systems ensures that only authorized users are able to access the system. Many authentication systems are built around three authentication factors: 1) Something you know, 2) Something you have, and 3) Something you are. Something you know may relate to knowledge that an authorized user has, but should not be available to others, such as a password or personal identification number (PIN). Something you have may refer to a physical object that is in the possession of the user. For example, a SecureID token from RSA™. Something you are may refer to immutable characteristics of a user, such as biometric identification information. For example, a user's fingerprints, retinal scans, or DNA are characteristics that may define the user and are difficult, if not impossible, to alter or reproduce. Authentication systems may utilize one, two, or three of these factors in order to properly authenticate users.